> For AI agents: the complete documentation index is available at https://viteval.dev/llms.txt, the full documentation bundle is available at https://viteval.dev/llms-full.txt.

# `wrapScorer()`

Transform the output or expected value before passing them to an existing scorer.
The wrapper preserves the scorer's name and forwards input and extra case fields.

## Import

```ts
import { wrapScorer } from 'viteval';
```

## Signature

```ts
function wrapScorer<
  OUTPUT,
  EXPECTED,
  INNER_OUTPUT = OUTPUT,
  INNER_EXPECTED = EXPECTED,
  EXTRA extends Extra = Extra,
>(
  scorer: Scorer<INNER_OUTPUT, INNER_EXPECTED, EXTRA>,
  options: WrapScorerOptions<OUTPUT, EXPECTED, INNER_OUTPUT, INNER_EXPECTED>
): Scorer<OUTPUT, EXPECTED, EXTRA>;
```

## Parameters


Parameters

scorerScorer<INNER_OUTPUT, INNER_EXPECTED, EXTRA>required

The scorer receiving the transformed values.

optionsWrapScorerOptionsrequired

Synchronous transformations. Omitted transformations pass the original value
through.

Properties

output(output: OUTPUT) => INNER_OUTPUToptional

Transform the task's output before scoring.

expected(expected: EXPECTED) => INNER_EXPECTEDoptional

Transform the dataset's expected value before scoring.

## Example

```ts
import { evaluate, scorers, wrapScorer } from 'viteval';

evaluate('Structured answer', {
  data: [{ input: 'What is 2 + 2?', expected: { answer: '4' } }],
  task: () => ({ text: '4' }),
  scorers: [
    wrapScorer(scorers.exactMatch(), {
      output: (value: { text: string }) => value.text,
      expected: (value: { answer: string }) => value.answer,
    }),
  ],
});
```

## Return value and errors

Returns a scorer with the outer `OUTPUT` and `EXPECTED` types. The inner scorer's
score and metadata are returned unchanged. Transformations are not awaited.
Exceptions propagate to the evaluator and fail the case.

See [createScorer()](https://viteval.dev/api/scoring/create-scorer.md) for the scorer callback contract.